The present invention relates to a rack-pinion type steering apparatus to be used for the wheels of motor vehicles or the like.
FIG. 7 is a front view, with portions broken away, of a rack-pinion type power steering apparatus of prior art, in which an auxiliary steering force is obtained by oil pressure. This steering apparatus comprises a steering shaft 92 connected to a steering wheel (not shown), a pinion 93 connected to the steering shaft 92, a rack 94 meshed with this pinion 93, a cylindrical metallic housing 95 in which the rack 94 is inserted, and a valve device 98 for supplying oil pressure, according to the steering force and the steering direction, to oil chambers 95a, 95b inside of the housing 95. Through ball joints 96, tie rods 97 are connected to the both ends of the rack 94 which project from the both ends of the housing 95. Wheels are connected to the tie rods 97 through knuckle arms (not shown) or the like. With the arrangement above-mentioned, when the pinion 93 is rotated by a steering operation, the rack 94 is axially moved to change the steering angle.
A ring-like end cap 101 is mounted at one end of the housing 95, and the rack 94 is slidably inserted in this end cap 101. This end cap 101 is inserted in the inner peripheral surface of the end portion of the housing 95. A cir-clip 102 wound on the outer periphery of the end cap 101, restrains the end cap 101 from being moved axially of the housing 95 (See FIG. 8). More specifically, annular grooves 103, 104 are oppositely formed respectively in the inner periphery of one end of the housing 95 and the outer periphery of the end cap 101, each annular groove 103, 104 having a depth substantially equal to a half of the diameter of the cir-clip 102 (See FIG. 9). The cir-clip 102 is inserted into the annular space defined by the annular grooves 103, 104, thus causing the end cap 101 to be engaged with the housing 95.
The cir-clip 102 is made of a metallic wire and has, as shown in FIG. 10 illustrating its free state before mounted, a linear winding portion 102a to be wound along the annular grooves 103, 104, and a hook portion 102b bent at one end of the winding portion 102a at a right angle thereto. The hook portion 102b is passed through an insertion opening 105 formed in the peripheral surface of the housing 95 and is hooked at an engagement groove 101b of the end cap 101 (See FIG. 11). At this state, the end cap 101 is rotated with a tool such that while being wound in the annular groove 104 of the end cap 101, the winding portion 102a of the cir-clip 102 is successively introduced inside of the housing 95 and is mounted in the space defined by the annular grooves 103, 104. At this time, the end cap 101 is rotated substantially by one and a half revolutions such that the hook portion 102b of the cir-clip 102 is located substantially at the opposite side of the insertion opening 105 with respect to the axis of the end cap 101 (See FIG. 8).
In the steering apparatus above-mentioned, the ball joint 96 strikes the end cap 101 to regulate the maximum steering angle position in one direction (rightward moving stroke of the rack 94 in FIG. 7). However, when the ball joint 96 strikes the end cap 101 with an excessive steering force applied to the rack 94, a relative twist occurs between the ball joint 96 and the rack 94. So, the end cap 101 may be slightly rotated together with the cir-clip 102. When the end cap 101 is repeatedly rotated, there are instances where the tip of the cir-clip 102 is moved up to the insertion opening 105 of the housing 95. This involves the likelihood that the tip of the cir-clip 102 springs out of the insertion opening 105 due to its spring back (See FIG. 12), that the subsequent portion is consecutively gradually springs out of the housing 95 (See FIG. 13), and that it becomes finally impossible to prevent the end cap 101 from being axially freely moved.
In this connection, provision is made as shown in FIGS. 14 and 15. That is, the other end of the cir-clip 102 is bent arcuately or linearly to form a bent portion 102e, and this bent portion 102e is resiliently mounted in the space defined by the annular groove 103 of the end cap 101 and the annular groove 104 of the housing 95, thus restraining the cir-clip 102 from being rotated.
However, the former arcuately bent portion 102e easily follows the annular grooves 103, 104. Accordingly, the bent portion 102e cannot strongly resiliently be mounted in the space between the annular grooves 103, 104. This introduces the problem that the end cap 101 is not effectively prevented from being rotated. Further, when the bent portion 102e is moved to the insertion opening 105 of the housing 95 in association with the rotation of the end cap 101, there are instances where the bent portion 102e runs onto the opening edge of the insertion opening 105 of the end cap 101 and springs out of the insertion opening 105. Accordingly, the cir-clip 102 cannot securely be prevented from springing out of the housing 95. The latter linearly bent portion 102e can strongly resiliently be mounted in the space between the annular grooves 103, 104, thus effectively preventing the end cap 101 from being rotated. However, stress concentration occurs at a bending starting point X. Therefore, the bending starting point X is disadvantageously readily broken and therefore poor in durability.
It is an object of the present invention to provide a rack-pinion type steering apparatus capable of securely preventing, for a long period of time, the cir-clip from springing out of the housing.
A rack-pinion type steering apparatus according to the present invention comprises: a pinion connected to a steering shaft; a rack meshed with the pinion; a cylindrical housing in which the rack is inserted; an end cap inserted into one end of the housing with the rack inserted in the housing; and a cir-clip interposed between an annular groove formed in the outer periphery of the end cap and an annular groove which is opposite to the first-mentioned annular groove and which is formed in the housing, the cir-clip being arranged to prevent the end cap from being moved axially of the housing, the cir-clip being provided at an end thereof with (i) an inwardly bent curved portion and (ii) a linear portion linearly extending inwardly from the tip of the curved portion and having a tip which always comes in contact with the bottom of the annular groove in the end cap.
According to the rack-pinion type steering apparatus having the arrangement above-mentioned, when the end cap is rotated to cause the curved portion and the linear portion to be moved to the insertion opening of the housing, the curved portion and the linear portion are restored substantially to the original shapes, and the curved portion and its vicinities project from the insertion opening. At this state, the tip of the linear portion is held as coming in contact with the bottom of the annular groove of the end cap. Accordingly, the tip side of the linear portion or the curved portion can selectively be engaged with the opening edge of the insertion opening according to the rotational direction of the end cap. This securely prevents the end cap from being rotated. Further, the curved portion prevents stress concentration from occurring at one end of the cir-clip. Thus, there is no danger of the cir-clip from being broken. It is therefore possible to securely prevent, for a long period of time, the cir-clip from springing out from the insertion opening.
In the rack-pinion type steering apparatus of the present invention, the curvature radius of the curved portion of the cir-clip in a free state (before the cir-clip is mounted in the space between the annular grooves), is preferably smaller than the curvature radius of the annular groove of the end cap.
According to the arrangement above-mentioned, the elastic rebound force of the curved portion can be increased, enabling one end of the cir-clip to be strongly resiliently mounted in the space between the annular groove in the end cap and the annular groove in the housing. This effectively prevents the end cap from being rotated. It is therefore possible to restrain, for a long period of time, the curved portion and its vicinities of the cir-clip from being moved to the insertion opening. Accordingly, the end cap can stably be engaged with the housing for a long period of time.